1. Field of the Invention
Embodiments of the invention relate to diffractive optical elements that have the dual properties necessary to focus and disperse an impinging optical wave, master devices for replicating the diffractive optical elements, and compact spectrometers including these optical elements.
2. Description of the Related Art
The optical spectrometer has become one of the most important and most widely used instruments in modern science and engineering. See J. James, Spectrograph Design Fundamentals (Cambridge University Press, Cambridge, 2007). It has found a myriad of applications in numerous areas such as material characterization, chemical sensing, and biomedical diagnostics. As optical spectroscopy continues to play a vital role in many of today's rapidly developing fields and with the boom of portable electronic industry (cell phones, laptop computers, etc.), there is a growing need for development of cost-effective and miniature spectrometers that can be potentially integrated with these portable electronics devices.
Despite a steady progress on the spectrometer performance, the use of discrete optical components (i.e., the collimating and collecting curved mirrors and the diffraction grating) has been a main reason that conventional optical spectrometers are usually bulky and costly. Various efforts have been made to address this issue. As a well-known example, concave gratings integrate the functions of the collimating and collecting curved minors as well as the diffraction grating in one device. See C. Palmer, and E. Loewen, Diffraction grating handbook (Newport Corporation, 2005). A volume holographic spectrometer has also been recently investigated, which can eliminate the entrance slit, collimating and collecting curved minors, as well as the grating all together with a volume hologram. See C. Hsieh, O. Momtahan, A. Karbaschi, and A. Adibi, Appl. Phys. B 91, 1 (2008). Other devices such as waveguide grating couplers and integrated micromechanical systems are known.